TITLE: GCN CIRCULAR NUMBER: 38112 SUBJECT: EP241107a: EP on-board trigger and autonomous follow-up observation DATE: 24/11/07 15:20:23 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

H. Zhou (PMO, CAS), R.-Z. Li (YNAO, CAS), W. Chen, T. Zhao (NAO,CAS), X. L. Chen (YNU), K. Chatterjee (YNU) and H. W. Pan (NAO,CAS) report on behalf of the Einstein Probe team:

We report on the detection of an X-ray transient detected by EP-WXT, EP241107a, which triggered the on-board processing unit at 2024-11-07T14:10:23Z (UTC) (trigger ID: 01709118091). The trigger flux is estimated to be around 1e-10 erg/s/cm^2 in 0.5-4 keV. An autonomous observation on the X-ray transient was performed by the EP-FXT about 5 minutes later, which detected an X-ray source at R.A. = 35.0085 deg, DEC = 3.3329 deg (J2000) with an uncertainty of about 10 arcsecs (radius, 90% C.L. statistical and systematic), consistent with the position of the WXT transient within the uncertainties.

In the image of DESI Legacy Imaging Surveys, there is a star (effective temperature is about 3600 K, from GAIA DR3) and a galaxy within the EP-FXT error circle of EP241107a. Hence, the possibility that EP241107a is a stellar flare event cannot be ruled out. Further follow-up observations are encouraged to explore the orgin of EP241107a.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).

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